Artificial underwater habitats

ABSTRACT

An artificial underwater habitat for crustacea comprising a plurality of tubular elements for a thermoplastic material having a density of 1.2 to 2, with the tubular elements having a flattened portion while allowing free flow of water therethrough.

United States Patent 1 Thomas et al.

[ 51 Dec. 30, 1975 ARTIFICIAL UNDERWATER HABITATS [75] Inventors: Jean-Claude Thomas, Neuilly/Seine',

Pierre Raoul, Epinay/Orge; Claude Ledoux, Massy, all of France [73] Assignee: Rhone-Progil, Courbevoie, France [22] Filed: June 17, 1974 [21] Appl. No.: 479,772

[30] Foreign Application Priority Data June 22, 1973 France .l 73.22836 [52] US. Cl. 119/2 [51] Int. Cl. AOIK 61/00 [58] Field of Search 119/2, 3,4; 6l/2l,4, 61/5, 3

[56] References Cited UNITED STATES PATENTS 3,658,034 4/1972 Day et al. 119/4 Primary Examiner-Russell R. Kinsey Assistant Examiner-Peter K. Skiff Attorney, Agent, or Firm-McDougall, Hersh & Scott [57] ABSTRACT An artificial underwater habitat for crustacea comprising a plurality of tubular elements for a thermoplastic material having a density of 1.2 to 2, with the tubular elements having a flattened portion while allowing free flow of water therethrough.

10 Claims, 3 Drawing Figures US. Patent Dec.30,1975

The present invention relates "to artificial habitats intended for the rearing or ranching o f crustacea, gen} erally on seabeds, and for protecting themagainst 'pre d ators and also to a method ofpreparingsu'ch habitats? In the copending application "Ser.'No';f454,236, filed Mar. 25,-1974, the applicants have described artificial habitats intended for the raising of fish and crustacea: on the seabed and for a method of preparing such habitats. Said habitats are constituted of a plurality of structures, which will be designated as structures A, formed of prismatic members wound into helical turns, and made of erosion-resistant and corrosion-resistant thermoplastics materials, having a density of from 1.2 to 2.

The arrangement upon seabeds of said A structures, most of which constitute the habitats, may vary depending upon the equatie species for which they are intended. In the case of crustacea, for example lobsters, a random stacking is recommended in order to provide a protection for the crustacea against predators, in particular conger eels.

The applicants have now found that a better protection for the crustacea against predators can be provided by means of artificial underwater habitats comprising a plurality of structures of thermoplastics material having a density of from 1.2 to 2, the structures comprising tubular elements, which are partially flattened at a point along their length, while allowing substantially free circulation of water inside the tubular elements.

The preferred values of the dimensional parameters which characterize these structures, such as the internal diameter D of the tubular elements, their thickness E and their length L, depend upon the state of development of the crustacea. There are favorable dimensions of the habitat corresponding to each stage of development. It is therefore especially advantageous to deposit, on the same site, structures of differing dimensions in order that the crustacea shall always be able to find habitats adapted to their size.

In preferred embodiments of the invention, the diameter D is from to 150 mm, the thickness E from 1.5 to 10 mm and the length L from 100 to 750 mm in the case where the tubular element forms a single habitat and from 200 to 1500 mm in the case where the tubular element forms a double habitat.

A random distribution of the structures according to the invention, optionally associated with A structures, is recommended.

The preparation of the tubular elements forming the B structures of the present invention may be carried out starting from a prismatic member produced by extrusion through a die of molten composition comprising at least one thermoplastics material and optionally a filler. Fly ash, such as that generated in municipal incinerators or thermal power stations may be used as filler. As it issues from the die, the prismatic member may be cut at regular intervals, and then each element obtained is locally and partially flattened so as to permit the free circulation of the water inside the tubular element.

Any thermoplastiematerial which, with or without fillers, is capable of producing prismatic members having a density of from 1.2 to 2, and notably polymeric or copolymeric compositions based upon vinyl chloride,

are suitable for the manufacture of the structures according to the invention.

An important economic advantage of the invention resides in the possibility and theadvantage of preparing the prismatic members from plastics waste materials, and especially fromindustrial waste. The exploitation of the inventionthus contributes bothto the disposal and. to the utilization of plastics, waste. Before being used in this way, the waste may, if necessary, be washed in water, crushed and then dried.

Embodiments ofthe invention will be illustrated by the following examples, in which'referenee is made to the drawing in which:

FIG. 1 is a sectional elevational view showing one embodiment of the invention;

FIG. 2 is a view similar to that of FIG. 1 showing another embodiment; and

FIG. 3 is a perspective view showing an arrangement of elements of FIG. 2 in forming a habitat.

EXAMPLE 1 Waste thermoplastics plate material based upon rigid polyvinyl chloride is crushed to form pieces of dimensions not exceeding 10 mm.

The material is extruded at 180C in a rotating plate extruder fitted with two plates of 180 mm diameter separated by a gap of 12 mm and with a tubular die. The speed of the revolving plate is 130 rpm. and the output rate is 120 kg/hour.

The tubular prismatic member obtained, having an internal diameter of mm and a thickness of 5 mm, is cut into elements 10 of 400 mm length, and are partially flattened at one of their ends 12. The structures thus obtained, when distributed on a seabed l4, constitute an artificial habitat suitable for the rearing of crustacea, such as lobsters, and for protecting them against predators.

EXAMPLE 2 The procedure of Example 1 is followed, but the tubular prismatic member obtained is cut into elements 20, 800 mm in length, which are partially flattened in the middle 22.

The structures obtained in this way, when distributed on a seabed 24, constitute an artificial habitat suitable for the rearing of crustacea, such as lobsters and for protecting them against predators.

We claim:

1. An artificial underwater habitat for crustacea comprising a plurality of unenclosed structures of thermoplastics material having a density of from 1.2 to 2 resting on the sea bed, the structures comprising relatively straight open ended tubular elements, which are partially flattened at a point along their length while allowing substantially free circulation of water inside the tubular elements.

2. A habitat according to claim 1, in which the internal diameter of the tubular elements is from 20 to 150 mm, the thickness of the wall of the elements is from 1.5 to 10 mm, the length of the elements is from to 750 mm and the elements are partially flattened at one end.

3. A habitat according to claim I, in which the internal diameter of the tubular elements is from 20 to I50 mm, the thickness of the wall of the elements is from L5 to 10 mm, the length of the elements is from 200 to 1500 mm and the elements are partially flattened at a point half-way along their length.

9. A habitat according to claim 5, in which the thermoplastics material comprises waste material.

10. A method of making an artificial habitat for crustacea, which comprises depositing on the seabed a plurality of structures of thermoplastics material having a density from 1.2 to 2, the structures comprising relatively straight open ended tubular elements which are partially flattened at a point along their length while allowing free circulation of water inside the tubular elements. 

1. An artificial underwater habitat for crustacea comprising a plurality of unenclosed structures of thermoplastics material having a density of from 1.2 to 2 resting on the sea bed, the structures comprising relatively straight open ended tubular elements, which are partially flattened at a point along their length while allowing substantially free circulation of water inside the tubular elements.
 2. A habitat according to claim 1, in which the internal diameter of the tubular elements is from 20 to 150 mm, the thickness of the wall of the elements is from 1.5 to 10 mm, the length of the elements is from 100 to 750 mm and the elements are partially flattened at one end.
 3. A habitat according to claim 1, in which the internal diameter of the tubular elements is from 20 to 150 mm, the thickness of the wall of the elements is from 1.5 to 10 mm, the length of the elements is from 200 to 1500 mm and the elements are partially flattened at a point half-way along their length.
 4. A habitat according to claim 1, in which the structures are randomly distributed underwater.
 5. A habitat according to claim 1, in which the tubular elements are extruded thermoplastics material.
 6. A habitat according to claim 5, in which said extruded plastic material contains a filler.
 7. A habitat according to claim 6, in which the filler is ash of municipal incinerators and thermal power stations.
 8. A habitat according to claim 5, in which the thermoplastics material comprises a polymeric or copolymeric composition based upon vinyl chloride.
 9. A habitat according to claim 5, in whicH the thermoplastics material comprises waste material.
 10. A method of making an artificial habitat for crustacea, which comprises depositing on the seabed a plurality of structures of thermoplastics material having a density from 1.2 to 2, the structures comprising relatively straight open ended tubular elements which are partially flattened at a point along their length while allowing free circulation of water inside the tubular elements. 